Constant pressure series of oxy-fuel cutting nozzles



Apfl'ifl 18, 1967 ANTHES ET AL 3,314,612

CONSTANT PRESSURE SERIES OF OXY-FUEL CUTTING NOZZLES Filed Oct. 21, 1964I/VI/EA/TOPS CLIFFORD C. ANTHES EDWARD MEINCKE JOHN VILLORESI UnitedStates Patent Ofiice 3,3 l4,612 Patented Apr. 18, 1967 3,314,612CONSTANT PRESSURE SERIES OF OXY-FUEL CUTTING NOZZLES Clilford C. Anthes,Union, Edward Meinclre, Summit, and John Villoresi, Lincoln Park, N..l.,assignors to Union Carbide Corporation, a corporation of New York FiledGet. 21, 1964, Ser. No. 407,270 2 Claims. (Cl. 239-580) This is acontinuation-in-part of Serial No. 101,805, filed April 10, 1961.

This invention relates to a constant pressure series of non-divergingcylindrical bore oxy-fuel cutting nozzles for selective use in a nozzleholder, and more particularly to a series of this character which iseffective in cutting metal stock having a wide range of thicknesses,when supplied with oxygen at the same pressure. Non-divergingcylindrical bore nozzles are most commonly used in hand cuttingoperations as contrasted with divergent bore nozzles which are usedalmost exclusively in machine cutting where the slag spatter normallyproduced thereby can be tolerated.

It has been widely recognized that there is an optimum volume flow ofcutting oxygen for cutting each thickness of metal. Thus, the mostefficient and economical oxygen cutting operations are obtained byhaving the diameter of the nozzle cutting oxygen bore tailored to theparticular metal thickness to be cut. Therefore, it has become commonpractice with producers of oxygen cutting torches to supply cuttingnozzles in series form. Such a series of nozzles, containing any-wherefrom 6 to 12 nozzle sizes, will include for example starting with thesmallest size, a nozzle having a .020 diameter cutting oxygen bore forcutting up .to /s" material, a nozzle having a .037" diameter cuttingoxygen bore for cutting up to /2" material, etc., up to the largest sizenozzle having a .144" diameter cutting oxygen bore for cutting up to 12"material. For each size of cutting oxygen bore of course a suitableoxygen operating pressure must be employed for delivering the requiredoxygen to the nozzle discharge orifice. In non-diverging cylindricalbore nozzles, these oxygen pressures will vary over a wide range, erg.from 30 p.s.i. for the smallest sizes up to 100 p.s.i. or more for thelargest sizes, whereas a divergent bore series will operate effectivelyover a much narrower pressure range. Thus, in order for the operator toobtain the optimum in cut quality and economy as to oxygen consumption,it is necessary for him to combine the proper size nozzle with theproper oxygen pressure for the particular material thickness to be out.

Tables of recommended operating pressures are generally supplied witheach cutting torch. Unfortunately, they are not always available whenneeded by the operator and, even when available, entail someinconvenience in referring to them. As a result, it has become commonpractice for the operator to rely on his own judgment and experience insetting his cutting oxygen pressures. Much waste, as Well as a loss incut quality, due to the use of excessive and unsuitable pressures hasresulted.

The most desirable solution to this problem, and the one provided bythis invention, is to have a whole series of non-divergent cylindricalbore nozzles, from the smallest size for cutting /s material to thelargest size for cutting up to 12" material, operate on one basiccutting oxygen pressure. Combine this with a metal thickness designationmarked on each nozzle indicating the metal thickness .that particularnozzle cutting oxygen bore has been tailored to cut, and the so-calledart is taken out of oxygen cutting operations. Even the mostinexperienced operator, merely by selecting the nozzle of the series ofthe invention bearing the proper metal thickness designation and settinghis cutting oxygen pressure to the one r or nodes to be formed in thekerf walls.

basic value, can obtain high quality cuts with kerfs, of minimum width,having smooth, vertical Wall faces.

In addition, We have found that the variation, from the smaller sizes tothe larger sizes of nozzles, in the Q/ A value of the cutting oxygenstream, which characterizes conventional cutting nozzle series, is aserious deterrent to achieving the optimum in cut quality and cuttingspeed for all thicknesses of material. (The Q/A value referred to hereinis a design reference utilized to establish the port size for a givenoxygen flow according to the well-known formula V=Q/A wherein V is thedesign reference number, Q denotes quantity of gas in cubic feet perhour, and A is the cross-sectional area in square inches of the portthrough which the measured fluid passes.) The Q/A value for mostconventional nozzle series varies over a range of anywhere from 25,000to 100,000.

We have found that a Q/A value for the cutting oxygen jet or stream ofapproximately 52,000 (45,000 to 60,000), maintained constant for allsizes of nozzles, provides the optimum in cut quality and cutting speedfor all thicknesses of material. If the Q/A value is above 60,000, theresulting over expansion of the oxygen stream as it emerges from thecutting oxygen port causes waves Thus, the desired uniformly smooth kerfwalls are not obtained. If the Q/A value is less than 45,000 the resultis a kerf which tends to undesirably converge or narrow down at thebottom. Thus, the kerf walls will not be straight, that is,perpendicular to the top surface of the metal plate being cut.

According to the present invention, a series of nondiverging cylindricalbore oxy-fuel cutting nozzles are provided for selective use in a nozzleholder. This series of nozzles is capable of effectively cutting metalstock having a wide range of metal thicknesses when supplied with oxygenat the same pressure. The range referred to is substantially larger thanwas heretofore possible using prior art nozzle series. Each tip of theseries has a nondiverging cylindrical discharge passage which is sizedto deliver .the required oxygen fiow for a given narrow range of metalthickness at a Q/A value of between 45,000 and 60,000 ft. /hr. x in.Each tip of the series also has an intermediate passage having aconverging tapered portion for delivering oxygen into the dischargepassage. Preferably, the diameter of the intermediate passage is atleast one and a half times the diameter of the discharge passage. Also,the tapered portion should preferably form an included angle of theorder of 15. Finally, each tip of the series has a metering orificeupstream of the intermediate passage. The metering orifice has a smallerdiameter than the intermediate passage to effect a fixed pressure drop.The diameter of the discharge passage of each tip in the series isincreased over the next smaller tip to provide the optimum flowconditions for a narrow rnetal thickness range, and the diameter of themetering orifice of each tip in the series is also increased inproportion to the increment of the corresponding discharge passage toprovide nozzles to effectively cut increased thicknesses of metal stockat one fixed supply pressure. Preferably, each metering orifice shouldhave a length to diameter ratio of between 2 /2 to 1 and 3 to 1.

Each nozzle thus cooperates with one or more other nozzles havingsimilarly arranged passages and adapted for installation on the sameblowpipe body, to form a set of interchangeable nozzles. Each nozzle ofthe set will cut a different narrow range of metal thickness at the sameoxygen supply pressure, and will do so with optimum effectiveness. Themetering orifice of each nozzle in the set is sized so as to deliver theoptimum oxygen flow through its respective nozzle discharge port whenthe nozzle inlet is supplied with oxygen at a pressure equal to thatwhich is supplied to the other nozzle or nozzles of the set.

In the design of the nozzle series of the invention,

. i In designing a series of nozzles which will (a) all operate from asingle constant cutting oxygen head pressure and (b) provide the optimumvolume flow of cutting oxygen for the particular metal thickness rangeof each basically we have combined: (a) a cutting oxygen port 5 nozzleof the series at a Q/A value of approximately tailored to deliver therequired cutting oxygen flow for 52,000, it is necessary first to selectthe proper cutting a given narrow range of metal thicknesses at aconstant oxygen port size for each nozzle and then combine this Q/ Avalue of approximately 52,000; (b) a metering orifice according to apredetermined relationship with a metering upstream of the cuttingoxygen port so sized with respect orifice located in the inlet of thenozzle cutting oxygen to the cutting oxygen port that the whole seriesof nozzles passage.

operates on one basic cutting oxygen pressure; and (c) a Knowing theoptimum cutting oxygen flow and the cutting oxygen passage design thatresults in an issuing desired Q/A value, it is a simple matter todetermine the oxygen stream that maintains its cylindrical shape andproper cutting oxygen port size using the equation diameter for asignificant distance beyond the end of the (1) V O/A nozzle. Thus, wehave not only taken the so-called art out of oxygen cutting operations,but further have ensured To establish C0r responding metering OrificeSize, it the achievement of consistently good quality, high speed isfirst necessary tO decide What Constant cutting Oxygfin cuts i h k f ofi i idth h i nif ly head pressure is to be used. In designing the nozzleseries Smooth, i 1 11 depicted in the foregoing table, 65 psi. waschosen as The single figure of the drawing is a longitudinal cross theconstant Cutting YE head Pressure for thme section through a nozzleshowing the characteristics of r s! the cutting oxygen passage of theseries according to the (1) It was found to be a high enough pressure tocut present i ti all thicknesses of metal up to 12 inches.

The cutting oxygen passage comprises metering orifice (2) It is asufficiently high pressure to ermit the use 10, intermediate portion 12,and cylindrical cutting oxyof divergent bore nozzles. for increasedcutting speed gen port 13, with a converging taper 14 of 15 degreesshould it be so desired. included angle as the transition fromintermediate por- (3) It is a pressure not in excess of the pressureavailtion 12 to port 13. able from the new LC3 type liquid oxygencylinder The ideal cutting nozzle series of course would include supply.

a nozzle in the series for every thickness of metal to be A secondfactor to be taken into consideration in cut. In this way, the cuttingoxygen bore could be establishing the upstream metering orifice size isthe tailored exactly as to volume flow of oxygen to suit the dischargecoeificient of the downstream oxygen port. metal thickness. From anoperating, as Well as manu- Where two orifices are used in series, thedischarge coefiifacturing standpoint, this is obviously impractical. Wecient of the downstream orifice has a marked effect on have found thatgood quality, economical oxygen cutting the selection of the proper sizeof the upstream orifice can be performed on metal ranging in thicknessfrom in order to achieve proper flow at the predetermined head to 12",using a nozzle series containing 12 sizes. pressure at the inlet of thefirst orifice. Therefore, in

The following table lists the 12 nozzle sizes representaestablishing theupstream metering orifice size, it is necestive of the nozzle series ofthe invention together with sary to know what the discharge coeflicientis in the the metal thickness range each size nozzle is designed todownstream orifice. The various factors which colleccut and the optimumcutting oxygen flow for each metal tively determine this dischargecoefficient, according to thickness range. well-known fluid flow theory,include:

Metal Thickness Cutting 02 Cutting 02 Intermediate Metering DimensionDimension Dimension Dimension Nozzle Size Range, in. Flow, c.1.h. Port13, Portion 12, Orifice 10, A, inches C, inch "6, inch D, inchesdia.-in. did-in. dia.-in.

15 0200 082 0180 2. 883 /54 250 3. 304 55 0370 082 0330 2. 883 042 2503. 304 02 .0402 082 0400 2. 525 254 250 3. 304 147 .0505 125 0405 2. 525/42 250 3. 304 180 0070 .125 .0550 2. 525 5. .250 3. 304 252 0810 .14050505 2. 335 542 .250 3. 304 331 0800 1400 0730 2. 335 0 16 255 3. 304408 0005 1405 0810 2. 330 an .200 3. 304 475 .1040 .187 0800 2. 330 w.328 3. 304 500 1200 .187 0000 2. 101 A6 .359 3. 304 745 1360 137 2. 1013. 304 850 1440 137 1.883 3. 304

Until recent years, the cost of oxygen was the controlling (1) The ratioof the diameter of the approach bore factor in determining the optimumvolume flow of oxygen to that of the downstream orifice, which should beat for a particular cutting application and oxygen consumpleast 1 /2to 1. (Ratio of bore 12 to discharge port 13 tion was kept as low aspossible commensurate with good as shown in the drawing.) out quality.Now, however, with labor costs becoming (2) The form of the transitionfrom the approach bore the largest single cost factor, cutting speed hasbecome to the orifice. That is, the approach to the orifice may thedominant consideration. Thus, for the most economibe sharp-edged,tapered or rounded. (As shown in the cal cutting operations, the cuttingoxygen flow requiredrawing, we use a 15 included taper 14 as ourapproach ments for each metal thickness are desirably based on to theoxygen port 13.) that volume flow of cutting oxygen which provides the(3) The length of the orifice. fastest cutting speeds commensurate withgood cut quality (4) The smoothness of the walls of the approach boreand narrow kerfs. The cutting oxygen flow figures given and the orifice.in the foregoing table represent what we have found to be These factorswill, of course, be established by the the optimum flows for cutting theindicated metal thickoxygen passage design and method of manufacturesenesses. lected. The coefficient of discharge for the particular oxygenpassage design utilized in the nozzle invention is approximately 0.9.

Knowing the discharge coefiicient of the downstream oxygen port ororifice and the area of this port, the known critical flow equation foroxygen is used to determine the absolute upstream pressure P needed toobtain the desired fiow. (The critical flow equation is used because inorder to achieve the desired high Q/A of 52,000, critical flow isrequired.) In this equation: Q is the optimum cutting oxygen flow incubic feet per hour of formula (1); A is the area in square inches ofthe downstream oxygen port; and (p is the coefficient of discharge ofthe downstream oxygen port. The absolute upstream pressure P fromEquation 2 will also be the absolute downstream pressure P on themetering orifice.

Now, using the known non-critical flow equation for oxygen whereinseries of the Q=the optimum cutting oxygen flow in cubic feet per houras used in Equations 1 and 2 P =P of Equation 2 P =constant cuttingoxygen head pressure absolute '=discharge coefficient of the meteringorifice the area A of the metering orifice may be derived. The discharge coefiicient similarly to the discharge coefficient of the oxygenport above, is a matter of design and can be selected as desired.

(e) Using Equation 2 Q=1057 A P and an oxygen port design having adischarge coeflicient =.9 to solve for P P ==50.9 p.s.i. absolute or36.2 psi. gauge (f) Using Equation 3 and a metering port design having adischarge coeflicient (,0'=O.9 and solving for A .286 7 7 1.286 [teal-lThe closest drill is a No. 60 having a .040" dia. and an area of 00125?sq. in.

The combination of Equations 1, 2, and 3 in the manner described abovethus provides a means of determining the proper combination of ametering orifice and cutting oxygen port for each nozzle of a serieswhich permits operation of the entire series on one basic cutting oxygenhead pressure to supply from each nozzle the optimum cutting oxygen flowat the optimum Q/A value for cutting a particular metal thickness range.

However, while the proper relationship between the metering orifice andoxygen port sizes is of vital importance in the design of the nozzleseries of the invention, other features incorporated into the oxygenpassage of these nozzles have a significant bearing on the high qualityand economy of the cutting operations performed therewith.

While the cutting speed and the volume of oxygen consumed are the moresignificant factors, the metal loss due to the width of the kerf,nevertheless, constitutes an important part of the cost of any cuttingoperation. Thus, keeping the kerf width to a minimum commensurate withthe thickness of metal being cut is a desirable contribution to theeconomy of oxygen cutting applications.

The minimum kerf widths achieved with the nozzles of the invention aredue to the fact that the oxygen stream issuing from the oxygen portsmaintains its cylindrical shape and diameter for a greater distance fromthe end of the nozzle than is true with conventional nozzles. That is,the coherence of the oxygen stream is maintained for a longer traveldistance rather than its being broken up due to turbulence and/orlateral expansion almost immediately upon exiting from the oxygen port.Thus, the kerf width which is governed by the diameter and shape of theoxygen stream, is kept to a minimum.

In addition, this coherence of the oxygen stream permits utilization ofthe maximum quantity of kinetic energy available in the oxygen stream atthe point of cutting instead of having a substantial part of this energydissipated through turbulence and lateral expansion. Thus, theefficiency of the cutting operation is increased.

The fact that the oxygen stream issuing from the oxygen port of thenozzle of the invention maintains its cylindrical shape and diameter andis not disrupted by turbulence and lateral expansion is due to theparticular combination of design features incorporated into'the oxygenpassage of the nozzle.

(1) A metering orifice 10 having a length to diameter ratio of 2 /2 upto 3 to 1.

(2) An intermediate portion 12 having a length to diameter ratio aslarge as possible.

(3) A tapered transition section 14 between the intermediate portion 12and the oxygen port 13. An included taper of approximately 15 ispreferred in order to achieve a high discharge coefficient (0.9) for theoxygen port 13.

The combination of the above has been found to result in an oxygen flowpattern having the evenness and smoothness approaching that ofstreamlined or laminar flow with a minimum of turbulence.

What is claimed is:

1. A non-diverging cylindrical bore blowpipe nozzle, which is correlatedin size with one or more other nozzles having similarly arrangedpassages and adapted for installation on the same blowpipe body, to forma set of interchangeable nozzles, each adapted to cut a different narrowrange of metal thickness, said nozzle having a cylindrical cuttingoxygen discharge port adapted to deliver a cutting oxygen flow for anarrow range of metal thickness at a constant Q/A value of 45,000 to52,000 ftfi/hr. per square inch of discharge port cross section, anintermediate passage of a diameter at least one and a half times thediameter of said discharge port and having a converging portion leadinginto said discharge port, and a metering orifice of smaller diameterthan said intermediate passage connecting the nozzle inlet with saidpassage, said metering orifice being sized to deliver said oxygen flowthrough said discharge port when said 7 3 nozzle inlet is supplied withoxygen at a predetermined 1,850,379 3/1932 Campbell 239419 fixedpressure. 1,958,741 5/1934 Campbell 239419 2. A blowpipe nozzlecomprising a cylindrical non- 2,638,159 5/1953 Winkelman et a1. 239-423diverging discharge passage, an intermediate passage hav- 2,861,900 11/1958 Smith et a1. ing a converging portion leading into said discharge 5passage, and a metering orifice of smaller diameter than F REIGN PATENTSsaid intermediate passage connecting the nozzle inlet with 420,5838/1953 Canada said intermediate passage, said metering orifice beingsized 820,578 8/1937 France to deliver a flow of between 45,000 to52,000 ft. /hr. per square inch of discharge passage cross section tosaid 10 O H R NC S intermediate passage at a glven Sup p 1y pressureAcetogan Gas Catalog, Copyright 1956 by the Aceto- Refefencgs Cit d b thE i gen Gas. C0., 20137 Sherwood St., Detroit 34, Mich.-

UNITED STATES PATENTS Pages 2447 1,097,263 5/1914 Reich 239 119 15EVERETT W. KIRBY, Primary Examiner.

1,602,320 10/1926 Bastions.

2. A BLOWPIPE NOZZLE COMPRISING A CYLINDRICAL NONDIVERGING DISCHARGEPASSAGE, AN INTERMEDIATE PASSAGE HAVING A CONVERGING PORTION LEADINGINTO SAID DISCHARGE PASSAGE, AND A METERING ORIFICE OF SMALLER DIAMETERTHAN SAID INTERMEDIATE PASSAGE CONNECTING THE NOZZLE INLET WITH SAIDINTERMEDIATE PASSAGE, SAID METERING ORIFICE BEING SIZED TO DELIVER AFLOW OF BETWEEN 45,000 TO 52,000 FT. 3/HR. PER SQUARE INCH OF DISCHARGEPASSAGE CROSS SECTION TO SAID INTERMEDIATE PASSAGE, AT A GIVEN SUPPLYPRESSURE.